PROJECT SUMMARY The goal of this project is to develop small non-coding RNA directed transcriptional gene silencing as a therapeutic modality for the treatment of HIV-1 infection. We have learned that small non-coding RNAs targeted to specific loci in the HIV-1 or CCR5 promoters can result in long-term stable epigenetic silencing of HIV-1 or CCR5. Notably, this form of silencing in the context of HIV-1 is refractory to viral mutation. We have also recently developed and humanized the Pddlp DNA excision machinery from Tetrahymina thermophila and found that this system can be used to excise those loci targeted for transcriptional silencing by the small non-coding RNA. The work proposed here will mechanistically validate several different complimentary approaches that may result in a novel therapeutic capable of regulating transcription or excision of HIV-1 or CCR5 in a long-term manner. These approaches center around 3 methods of targeted delivery: (1) conditionally replicating HIV-2 vectors, (2) CCR5 or gp120 binding aptamers and (3) CXCR4 or CCR5 binding nanoparticles, in order to introduce non-coding RNAs and excision complex capable of transcriptionally silencing and excising HIV-1 or CCR5 in HIV-1 infected and relevant cell types. These approaches will be developed and mechanistically validated in vitro and in vivo as well as critically assessed for unintended secondary off-target effects. This proposal will be the first stage of validating several targeted delivery approaches to be used as a cell specific delivery strategy for non-coding RNA directed transcriptional gene silencing and RNA directed gene excision, a mechanism that has the potential to result in long-term stable silencing of viral expression in infected individuals in the absence of viral resistance.